Re: extended operator classes vs. type interfaces

On Fri, 2010-04-09 at 12:50 -0500, Kevin Grittner wrote:
> I just thought that if you were adding more type information,
> oriented aournd the types themselves rather than index AMs, some form
> of inheritence might fit in gracefully.

There are already some specific proposals for inheritance in database
theory literature. For instance: "Databases, Types, and the Relational
Model" by C.J. Date addresses inheritance explicitly (and the appendices
have some interesting discussion).

I'm not sure how compatible it is with SQL, though; and I am not very
optimistic that we could accomplish such a restructuring of the type
system while maintaining a reasonable level of backwards compatibility.

Either way, I think it's a separate topic. Two types that are not
related by any subtype/supertype relationship (like strings and ints)
can conform to the same interface (total ordering); while the very same
type can conform to two different interfaces.

Regards,
Jeff Davis